Content is now organized by game version and source

This link potentially matches multiple versions of "Nightmare":

• Nightmare (System Reference Document 5.2)

  CR 3 · Fiend (Large)

• Nightmare (System Reference Document 5.1)

  CR 3 · Fiend (Large)

• Nightmare (Monstrous Menagerie)

  CR 3 · Fiend (Large)

• Nightmare (Black Flag SRD)

  CR 3 · Fiend (Large)